From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760251AbYDCCET (ORCPT ); Wed, 2 Apr 2008 22:04:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757845AbYDCCEJ (ORCPT ); Wed, 2 Apr 2008 22:04:09 -0400 Received: from mga01.intel.com ([192.55.52.88]:16487 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757581AbYDCCEI (ORCPT ); Wed, 2 Apr 2008 22:04:08 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.25,596,1199692800"; d="scan'208";a="544700239" Subject: Re: rc6+ regression - backlight reset to 0 on boot after 7c0ea45be4f114d85ee35caeead8e1660699c46f From: Zhao Yakui To: Andrey Borzenkov Cc: "Rafael J. Wysocki" , linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <200804022253.17862.arvidjaar@mail.ru> References: <200804022253.17862.arvidjaar@mail.ru> Content-Type: text/plain Date: Thu, 03 Apr 2008 09:59:39 +0800 Message-Id: <1207187979.25346.8.camel@yakui_zhao.sh.intel.com> Mime-Version: 1.0 X-Mailer: Evolution 2.8.0 (2.8.0-7.fc6) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2008-04-02 at 22:53 +0400, Andrey Borzenkov wrote: > Commit 7c0ea45be4f114d85ee35caeead8e1660699c46f registers ACPI backlight > even if _BQC method (query current backlight level) is missing. The effect is: > > during initialization video.c:acpi_video_device_find_cap() calls backlight_update_status(). It tries to fetch actual level via acpi_video_get_brightness() - but as _BQC is missing it just returns current value > as stored in memory - i.e. zero, because it was never set. So effectively > backlight_update_status() reset brightness to minimal value == 0. > > This happens on Toshiba Portege 4000. Verified by reverting commit on top of > rc8. It seems that _BQC object is missing on the Toshiba Portege 4000. And acpi video driver will continue to update the status of backlight even when _BQC object is missing, which is inappropriate. Maybe it is more appropriate that OS doesn't update the status of backlight in boot phase when _BQC object is missing. Of course please attach the output of acpidump in kernel bugzilla. http://bugzilla.kernel.org/show_bug.cgi?id=10387 > On a side note, it would be nice to fit backlight device into actual ACPI > device tree instead of /devices/virtual.